Optical apparatus and image-pickup apparatus

ABSTRACT

An optical apparatus capable of reducing processing burden on the controller and achieving high-speed driving and improvement of the resolution of stop positions of an optical element. The optical apparatus includes a drive unit that drives the optical element, an operation member manually operated to instruct driving of the optical element and a signal output unit that outputs a signal that varies periodically according to the operation of the operation member. The controller determines the operation speed of the operation member based on the signal from the signal output unit, and chooses whether to control the drive unit according to the operation speed based on a count of periodic variations of the signal from the signal output unit, or to control the drive unit based on a value of the signal from the signal output unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical apparatus that detects anoperation of an operation member using a magneto-resistive (MR) elementand optical sensor, etc., and controls the driving of an opticalelement, and to an image-pickup apparatus using this optical apparatus.

2. Description of the Related Art

A lens apparatus (optical apparatus) used for an image-pickup apparatussuch as a video camera or digital still camera may be provided with amanual operation ring that gives drive instructions to a drive unit of avariable-power optical element or focusing optical element. In thiscase, a controller detects an amount of operation or operation directionof the manual operation ring and controls a driving operation of thedrive unit, that is, the optical element, according to the detectionresult.

As an example of a drive control system for optical elements using sucha manual operation ring, there is a system constructed of a magneticscale made up of different magnetic poles, which are arranged withalternating magnetic polarities, and a magnetic sensor facing thismagnetic scale in such a way as to move relative to each other inaccordance with operation of the manual operation ring, and to control adrive unit based on a count (count value) of a periodic variation(pulse) of a signal output from the magnetic sensor.

FIG. 7 shows an example of a control system utilizing a pulse count of amagnetic (MR) sensor. Reference numerals 20 a and 20 b in the figuredenote output signals of phase A and phase B from the MR sensor, as itmoves relative to a magnetic scale, and 20 c denotes a referencepotential of the controller.

The controller converts the output signals 20 a and 20 b, output fromthe MR sensor in accordance with operation of the manual operation ring,to digital (pulse) signals such as 20 d (phase A) and 20 e (phase B),counts cross points 20 f at which the pulse signals 20 d and 20 e crossthe reference potential 20 c, and controls the drive unit based on thecount value.

FIG. 8 illustrates an example of a control system that divides theoutput signal of the MR sensor at intermediate positions arbitrarily(intermediate separation control system). Reference numerals 20 a and 20b denote output signals of phase A and phase B from the MR sensor as itmoves relative to the magnetic scale, and 20 c denotes a referencepotential of the controller.

The controller extracts a portion 20 h of good linearity (20 f is anupper threshold of the linear portion 20 h, and 20 g is a lowerthreshold of the linear portion 20 h) of the output signals 20 a and 20b from the MR sensor, and divides this linear portion 20 h by anarbitrary number, for example, 20 or 50. Then, the controller controlsthe drive unit based on the signal value obtained during operation ofthe manual operation ring.

In order to improve resolution of the stop position of a variable-poweroptical system or a focusing optical system, it is necessary to improvedetection resolution of the rotation position of the manual operationring. Here, according to a pulse count control system using the MRsensor, the resolution of the rotation position of the manual operationring is determined by the pitch of a detection magnet of the MR. sensor.For this reason, improving the resolution of the rotation positionrequires the magnet pitch to be reduced.

However, there is a limit to work (manufacture) for reducing the magnetpitch and it is difficult to further reduce the actual pitch. Thus, itis difficult to drastically improve the resolution of the rotationposition of the manual operation ring. It is also possible to consider amethod that provides several stages of gear between the manual operationring and the magnetic scale to mechanically improve the resolution, butthis would lead to an increase in size of the apparatus.

On the other hand, the control system realized through intermediatedivision of the output signal of the MR sensor improves the resolutionbut complicates the processing of the control circuit and slows down theprocessing speed. Moreover, the user rotates the manual operation ringat high speed mostly for the purpose of moving optical elements close toa desired position at high speed without questioning segmentation of theresolution of stop positions of the optical element.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an opticalapparatus, and an image-pickup apparatus provided with this opticalapparatus, capable of reducing the processing burden on a controller,driving the optical element at high speed and improving the resolutionof stop positions.

In order to attain the above-described object, the optical apparatus,which is one aspect of the present invention, includes a movable opticalelement, a drive unit that drives the optical element, an operationmember manually operated to instruct a driving operation of the opticalelement, a signal output unit that outputs a signal that variesperiodically according to operation of the operation member, and acontroller that controls the drive unit based on a signal from thesignal output unit. The controller determines the operation speed of theoperation member based on the signal from the signal output unit, anddetermines whether to control the drive unit based on a count ofperiodical variations of the signal from the signal output unit or tocontrol the drive unit based on the value of the signal from the signaloutput unit.

Furthermore, an image-pickup apparatus of the present invention includesthe optical apparatus constructed as described above and a photoelectricconversion element that photoelectrically converts the image of anobject formed by the optical apparatus.

The features of the optical apparatus and image-pickup apparatus of thepresent invention will become more apparent with reference to thefollowing detailed description of preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a lens apparatus, which is anembodiment of the present invention;

FIG. 2 is a sectional view of the periphery of an MR unit of the lensapparatus shown in FIG. 1;

FIG. 3 is a front sectional view of the periphery of the MR unit of thelens apparatus shown in FIG. 1;

FIG. 4 is a block diagram of an electric circuit of an image-pickupapparatus provided with the lens apparatus shown in FIG. 1;

FIG. 5 is a flow chart showing a processing operation of the CPU of theimage-pickup apparatus provided with the lens apparatus shown in FIG. 1;

FIG. 6 is a schematic view of an optical sensor unit used in the lensapparatus in FIG. 1;

FIG. 7 illustrates an output signal of an MR sensor and pulseconversion; and

FIG. 8 illustrates intermediate division processing of the output signalof the MR sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to the attached drawings, embodiments of the presentinvention will be explained below.

(Embodiment I)

FIG. 1 shows a lens apparatus (optical apparatus), which is anembodiment of the present invention. As shown in FIG. 1, this lensapparatus has four lens units having convex, concave, convex and convexoptical power in that order from an object side to an image plane sideand constitutes an image-taking lens section of an image-pickupapparatus, such as a video camera or a digital still camera.

In FIG. 1, reference numeral L1 denotes a fixed first lens unit, L2denotes a second lens unit that performs variable-power operation bymoving in the direction of the optical axis L of the lens apparatus, L3denotes a fixed third lens unit and L4 denotes a fourth lens unit thatperforms focus adjustment operation (or image plane transfer correctionoperation accompanying power variation) by moving in the direction ofthe optical axis L.

Reference numeral 1 denotes a fixed lens barrel that holds the firstlens unit L1, 2 denotes a second lens unit holding member that holds thesecond lens unit L2, 3 denotes a third lens unit holding member thatholds the third lens unit L3, 4 denotes a fourth lens unit holdingmember that holds the fourth lens unit L4, and 5 denotes a rear lensbarrel that holds an image-pickup element (indicated by referencenumeral 45 in FIG. 4), which is a photoelectric conversion element suchas CCD or CMOS sensor.

The fixed lens barrel 1 and rear lens barrel 5 align and fix two guidebars 7 and 8. The lens unit holding member 2 is supported by the guidebars 7 and 8 in a manner movable in the direction of the optical axis L.

The third lens unit holding member 3 and rear lens barrel 5 align andfix two guide bars 9 and 10. The fourth lens unit holding member 4 issupported by the guide bars 9 and 10 in a manner movable in thedirection of the optical axis L. Furthermore, the third lens unitholding member 3 is aligned with and fixed to the rear lens barrel 5 viascrews 3 a.

Reference numeral 6 denotes a diaphragm unit that changes the apertureof the image-taking optical system; in this embodiment, the diaphragmunit 6 is a so-called iris type diaphragm that changes the aperture byopening/closing six diaphragm blades. This diaphragm unit 6 is fixed tothe rear lens barrel 5 via screws 6 a.

The fixed lens barrel 1 is aligned with the rear lens barrel 5 and fixedto the rear lens barrel 5 via screws 1 a.

Reference numeral 12 denotes a stepping motor unit (focus drive unit)that drives the fourth lens unit holding member 4 in the direction ofthe optical axis L, and has a lead screw 12 a integrally formed with itsoutput axle. The lead screw 12 a is engaged with a rack 4 a mounted onthe fourth lens unit holding member 4. Thus, when the stepping motorunit 12 rotates, the fourth lens unit holding member 4 is driven in thedirection of the optical axis L, guided by the guide bars 9 and 10, bymeans of engagement action between the lead screw 12 a and rack 4 a.

Furthermore, the fourth lens unit holding member 4, guide bar 10, rack 4a and lead screw 12 a are pressed against one another by a spring forceof a torsion coil spring 4 b, so as to eliminate backlash therebetween.

Reference numeral 13 denotes a stepping motor unit (variable-power driveunit) that drives the second lens unit holding member 2 in the directionof the optical axis L, and has a lead screw 13 a integrally formed withits output axle. The lead screw 13 a is engaged with a rack 2 a attachedto the second lens unit holding member 2. Thus, when the stepping motorunit 13 rotates, the second lens unit holding member 2 is driven in thedirection of the optical axis L, guided by the guide bars 7 and 8, bymeans of engagement action between the lead screw 13 a and rack 2 a.

Furthermore, the second lens unit holding member 2, guide bar 8, rack 2a and lead screw 13 a are pressed against one another by a spring forceof a torsion coil spring 2 b, so as to eliminate backlash therebetween.

These stepping motor units 12 and 13 are fixed to the rear lens barrel 5via screws (not shown).

Reference numeral 14 denotes a focus reset switch made up of aphoto-interrupter. The fourth lens unit holding member 4 that moves inthe direction of the optical axis L is provided with a plate-shapedlight shielding section (not shown), and the focus reset switch 14switches between a light-shielded state and a light transmitting statecaused by the light shielding section going in and out between thelight-emitting section and light-receiving section of the focus resetswitch 14. The focus reset switch 14 outputs an electric signal inaccordance with these states. This allows the controller, which will bedescribed later, to detect whether the fourth lens unit L4 is located ata reference position or not. The focus reset switch 14 is fixed to therear lens barrel 5 via screws 14 b through the substrate 14 a.

Reference numeral 15 denotes a zoom reset switch made up of aphoto-interrupter. The second lens unit holding member 2 that moves inthe direction of the optical axis L is provided with a plate-shapedlight shielding section 2 c, and the zoom reset switch 15 switchesbetween a light-shielded state and a light transmitting state caused bythe light shielding section 2 c going in and out between thelight-emitting section and light-receiving section of the zoom resetswitch 15. The zoom reset switch 15 outputs an electric signal inaccordance with these states. This allows the controller, which will bedescribed later, to detect whether the second lens unit L2 is located ata reference position or not.

The zoom reset switch 15 is fixed to the rear lens barrel 5 via screws15 b through the substrate 15 a.

Reference numerals 27 and 28 denote a manual focus ring and a manualzoom ring (both are operation members), respectively. The manual focusring 27 is disposed on the outer circumference of the intermediate lensbarrel 29 and front holding member 31. The manual zoom ring 28 isdisposed on the outer circumference of the intermediate lens barrel 29and rear holding member 30.

FIG. 2 and FIG. 3 show a configuration of the MR unit (signal outputunit) used to detect an amount of operation and operation direction ofthe manual focus ring 27 and manual zoom ring 28 in this embodiment.FIG. 2 shows a side sectional view of the periphery of the MR unit, andFIG. 3 shows a front sectional view of the periphery of the MR unitviewed from the direction indicated by an arrow A in FIG. 2.

In FIGS. 2 and 3, the manual focus ring 27 is disposed on the outercircumference of the intermediate lens barrel 29 and front holdingmember 31, and is sandwiched between the intermediate lens barrel 29 andfront holding lens barrel 31 with a minimum necessary clearance forrotation, such that the manual focus ring 27 is prevented from anyexcessive movement in the direction of the optical axis L.

Likewise, the manual zoom ring 28 is disposed on the outer circumferenceof the intermediate lens barrel 29 and rear holding member 30, and issandwiched between the intermediate lens barrel 29 and rear holding lensbarrel 30 with a minimum necessary clearance for rotation, such that themanual zoom ring 28 is prevented from any excessive movement in thedirection of the optical axis.

Reference numeral 33 denotes a rubber ring to prevent a user's hand,which manually operates the manual focus ring 27, from slipping, and 34denotes a rubber ring to prevent the user's hand, which manuallyoperates the manual zoom ring 28, from slipping.

The MR units for the manual focus ring 27 and manual zoom ring 28 havethe same structure as one another.

The MR unit is constructed of a disk-shaped magnetic scale 21 and MRsensors (MR sensor 22F for the manual focus ring 27 and MR sensor 22Zfor the manual zoom ring 28) placed facing each other with apredetermined space between the two on a portion of the outercircumference of this magnetic scale 21. In the center of the magneticscale 21, an axial member 25 is placed by means of press fitting orbonding in such a way as to be rotatable together with the magneticscale 21. The axial member 25 is supported by a front bearing 24 andrear bearing 35 provided for a transverse U-shaped casing member 23 in arotatable manner. The casing member 23 is fixed to the intermediate lensbarrel 29. Furthermore, a gear member 26 is attached to the axial member25 by means of press fitting or bonding in such a way as to be rotatabletogether with the axial member 25.

Internal tooth gear sections 27 a and 28 a are formed at the innercircumferences of the manual focus ring 27 and manual zoom ring 28, andgear members 26 are engaged with these internal tooth gear sections 27 aand 28 a. Thus, when the manual focus ring 27 or manual zoom ring 28rotates, the gear member 26 of the respective MR unit on the rotatingside rotates, the rotation is transmitted to the magnetic scale 21through the axial member 25, and the magnetic scale 21 rotates.

This causes the magnetic scale 21 to rotate and move with respect to theMR sensor (the magnetic scale 21 moves relative to the MR sensor) andthe MR sensor outputs electric signals (20 a, 20 b) with phase A andphase B, as shown in FIG. 7.

FIG. 4 shows a structure of an electric circuit of an image-pickupapparatus provided with the lens apparatus of this embodiment.

Reference numeral 40 denotes a controller made up of a CPU or MPU, etc.,and controls the overall image-pickup apparatus including theabove-described image-taking lens section (lens apparatus). Furthermore,the controller 40 captures signals output from the MR sensors 22F and22Z and performs operation processing on the output signals. Referencenumeral 45 denotes the aforementioned image-pickup element, whichphotoelectrically converts optical images of an object formed by thelens units L1 to L4. The output signal from the image-pickup element 45is sent to an image processing circuit (not shown), subjected to variousprocessing, transformed into image information, and then recorded in arecording medium, such as a semiconductor memory, optical disk or tape,by a recording section (not shown). Reference numerals 42 and 43 denotedriver circuits that drive the stepping motor units 12 and 13 inaccordance with drive signals from the controller 40.

Here, the processing operation based on the output signal from the MRsensors 22F and 22Z at the controller 40 will be explained using theflow chart in FIG. 5.

First, in step (abbreviated as “S” in the figure) 1, the output signal(20 a, 20 b in FIG. 7) from the MR sensor is captured. The output signalhere refers to the output signal from the MR sensor, that is, either theMR sensor 22F or 22Z, in accordance with operation of manual focus ring27 or manual zoom ring 28. The output signal is converted to pulses 20 dand 20 e shown in FIG. 7.

Then, in step 2, it is determined whether a signal corresponding to onepulse (alternatively, a plurality of pulses can be used) is output fromthe MR sensor within a predetermined time or not. When the signalcorresponding to one pulse is output, that is, when it is determinedthat the manual focus ring 27 or manual zoom ring 28 is operated at aspeed faster than the speed (predetermined speed) at which one pulse isoutput from the MR sensor within the above-described predetermined time,the process moves on to step 3. On the other hand, when the signaloutput from the MR sensor within the above-described predetermined timeshows a signal variation less than one pulse (when there is not a signaloutput corresponding to one pulse in the predetermined time), that is,when it is determined that the manual focus ring 27 or manual zoom ring28 has been operated at speed lower than the above-describedpredetermined speed, the process moves on to step 5.

In step 3, the number of pulses (digital signal) obtained by convertingthe output signal from the MR sensor, that is, the number of times theoutput signal from the MR sensor varies periodically, is counted. Then,in step 4, a driving operation of the focus drive stepping motor unit 12(that is, fourth lens unit L4) or zoom drive stepping motor unit 13(that is, second lens unit L2) is controlled based on the pulse countvalues.

More specifically, the controller 40 multiplies the pulse count value bya predetermined amount of motor drive or a predetermined amount of lensdrive per one pulse and rotates and drives the stepping motor unit bythe amount of rotation corresponding to the calculated target amount ofdriving. In this case, the controller 40 sends a drive signal to thedriver circuit 42 or 43 (shown in FIG. 4), and the driver circuit thatreceives this drive signal drives the corresponding stepping motor unitbased on the drive signal.

This causes the fourth lens unit L4 or second lens unit L2 to be drivenat high speed corresponding to the high speed operation of the manualfocus ring 27 or manual zoom ring 28. Then, the process moves on to step7.

On the other hand, in step 5, the linear portion (portion 20 h shown inFIG. 8) of the output signal (analog signal) from the MR sensor withgood linearity is divided by a predetermined number (that is,intermediate division). Then, the process moves on to step 6, where thefocus drive stepping motor unit 12 or zoom drive stepping motor unit 13is driven and controlled based on the analog value of the MR sensoroutput at that point of time.

More specifically, the controller 40 multiplies the analog valueobtained by a predetermined amount of motor drive or an amount of lensdrive per unit analog value and rotates and drives the stepping motorunit by the amount of rotation corresponding to the calculated targetamount of driving. In this case, the controller 40 sends a drive signalto the driver circuit 42 or 43 (shown in FIG. 4), and the driver circuitthat receives the drive signal drives the corresponding stepping motorunit 12 based on the drive signal.

This causes the fourth lens unit L4 or second lens unit L2 to be drivenat low speed corresponding to the low-speed operation of the manualfocus ring 27 or manual zoom ring 28 with high position resolution.Then, the process moves on to step 7.

In step 7, it is further determined whether there is an output signalfrom the MR sensor or not, and if there is an MR sensor output, theprocess moves back to step 2; if there is no MR sensor output, theprocess moves on to step 8, and finishes the driving control operationover power variation or focus driving.

This embodiment has described the case where it is determined whetherthe manual focus ring 27 or manual zoom ring 28 has been operated fasteror slower than a predetermined speed depending on whether a signalcorresponding to one pulse (or a plurality of pulses) is output from theMR sensor within a predetermined time. However, it is also possible touse a different method to determine the operation speed of the manualfocus ring 27 or manual zoom ring 28.

For example, FIG. 6 shows an optical sensor unit that can replace the MRsensor. Reference numeral 62 denotes a ring-shaped optical scale thatrotates in accordance with operation of the manual focus ring or manualzoom ring, and a reflecting surface whose shape (orientation) variesperiodically in the circumferential direction is formed on the outercircumference thereof. Reference numeral 61 denotes an optical encoderwhich has a light-emitting section and light-receiving section. Theoptical encoder 61 emits light from the light-emitting section onto thereflecting surface of the optical scale 62 and outputs an electricsignal corresponding to the amount of light reflected on the reflectingsurface and incident on the light-receiving section. When the opticalscale 62 rotates and the position of light emitted from the opticalencoder 61 on the reflecting surface changes, the amount of lightreceived by the light receiving section of the optical encoder 61 variesperiodically; therefore, by a shaping process of the electric signaloutput from the optical encoder 61, it is possible to obtain an outputsignal which varies periodically, or in a sine wave form, in the sameway as the output signal from the MR sensor.

Thus, depending on whether a signal corresponding to one pulse (or aplurality of pulses) is output from the optical sensor unit within apredetermined time or not, it is possible to determine whether themanual focus ring or manual zoom ring has been operated faster or slowerthan a predetermined speed.

This embodiment has described the case where a target amount of drive ofthe stepping motor is obtained through calculations, but it is alsopossible to store a target amount of driving corresponding to a pulsecount value or analog value in a memory as map data, and to read atarget amount of driving from the memory.

Furthermore, this embodiment has described the case where the magneticscale (or optical scale) rotates with respect to the fixed MR sensor (oroptical encoder) through operations of the manual focus ring and manualzoom ring, but the present invention can also adopt a configuration inwhich the MR sensor (or optical encoder) moves with respect to the fixedmagnetic scale (or optical scale) through operations of the manual focusring and manual zoom ring. Furthermore, this embodiment has describedthe case where a ring-shaped scale (magnetic or optical scale) is usedfor a signal output unit, but it is also possible to use a scale havinga shape other than a ring shape. For example, a flat-shaped orpolygon-shaped scale can be used.

Furthermore, this embodiment has described the case of a lens apparatushaving a variable-power optical system in a structure with four lensunits of convex, concave, convex and convex lenses, but the presentinvention is also applicable to a lens apparatus having a differentoptical system configuration.

As explained above, according to this embodiment, when the operationmember (manual focus ring or manual zoom ring) is operated faster than apredetermined speed, the drive unit is not controlled based on the valueof a signal output from the signal output unit (magnetic sensor oroptical encoder), but rather the drive unit is controlled based on thecount of periodic variations of the signal, which makes it possible todrive the optical element at high speed and reduce the processing burdenon the controller. On the other hand, when the operation member isoperated slower than the predetermined speed, the drive unit iscontrolled based on the value of the signal output from the signaloutput unit, and therefore it is possible to improve the resolution ofstop positions of the optical element.

While preferred embodiment has been described, it is to be understoodthat modification and variation of the present invention may be madewithout departing from scope of the following claims.

What is claimed is:
 1. An optical apparatus comprising: a movableoptical element; a drive unit that drives the optical element; anoperation member manually operated to instruct driving of the opticalelement; a signal output unit that outputs a signal that variesperiodically in accordance with operation of the operation member; and acontroller that controls the drive unit based on the signal from thesignal output unit, wherein the controller determines the operationspeed of the operation member based on the signal from the signal outputunit, and chooses whether to control the drive unit according to theoperation speed based on a count of periodic variations of the signalfrom the signal output unit, or to control the drive unit based on thevalue of the signal from the signal output unit.
 2. The opticalapparatus according to claim 1, wherein when the operation speed of theoperation member is faster than a predetermined speed, the controllercontrols the drive unit based on the count of periodic variations of thesignal from the signal output unit, and when the operation speed isslower than the predetermined speed, the controller controls the driveunit based on a value of the signal from the signal output unit.
 3. Theoptical apparatus according to claim 2, wherein when the operation speedof the operation member is slower than the predetermined speed, thecontroller controls the drive unit based on a value obtained throughintermediate division of the signal from the signal output unit.
 4. Theoptical apparatus according to claim 1, wherein the optical elementperforms power variation by moving in a direction of the optical axis ofthe optical apparatus.
 5. The optical apparatus according to claim 1,wherein the optical element adjusts focusing by moving in a direction ofthe optical axis of the optical apparatus.
 6. An image-pickup apparatuscomprising: the optical apparatus according to claim 1; and aphotoelectric conversion element that photoelectrically converts anoptical image formed by the optical apparatus.